Maryland Geological Survky 279 



the Lakota formation in the Black Hills region and from the Kootanie 

 formation of Montana. It is represented in the Virginia area by quite 

 a large number of mostly fragmentary specimens showing slight varia- 

 tions in the character of tlie pinnule-lobes or teeth which were made the 

 basis for distinguishing eight species by Professor Fontaine. It is pos- 

 sible that more than one type is included in the species as defined by the 

 writer, the nature of the material rendering certainty out of the question, 

 but if the test of the validity of a species be the possibility of its being 

 recognized a second time by either the original author or other students, 

 it must be admitted that these eight so-called species are not good species. 



Onychiopsis hrevifolia differs from Onychiopsis Goepperti and psilo- 

 toides principally in the smaller fronds, less robust pinnules, which 

 are also less ascending, and in the much less elongate character of the 

 pinnae and especially the pinnules. It is a much smaller and less robust 

 form than OnycMopsis latiloha, from which it is readily distinguished, 

 but approaches somewhat close to Onychiopsis nervosa. The latter 

 species is on the whole a larger fomi with less elongate and more tri- 

 angular pinnge, and the pinnules have more entire margins, the lobes 

 or teeth being rounded and not angular. The veins are also more 

 numerous. 



Occurrence. — Patuxent Formation. Fredericksburg, Dutch Gap, 

 Potomac Eun, Telegraph Station (Lorton), A'^irginia. 



Collection. — IT. S. National Museum. 



Onychiopsis nervosa (Fontaine) Berry 



Plate XXXVI, Figs. 1-6 



Thyrsopteris nervosa Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 1889, 



p. 122, pi. XXV, figs. 4, 5, 16; pi. xxxvii, figs. 2, 4; pi. xxxix, fig. -5; pi. 



xl, fig. 6. 

 Thyrsopteris Meekiana Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 1889, 



p. 125, pi. xxxviii, figs. 2-4, 8; pi. 1, figs. 7, 8; pi. li, fig. 3. 

 Thyrsopteris crassinervis Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 



1889, p. 130, pi. xli, figs. 1-3. 

 Thyrsopteris pecopteroides Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 



1889, p. 135, pi. li, fig. 1. 

 Thyrsopteris heteroloha Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 



1889, p. 139, pi. liii, fig. 4. 



